Photocurable resins which are transparent or translucent, radioopaque, have good workability, and have good mechanical strength and stability are useful in medical, dental, adhesive, and stereolithographic applications.
Low polymerization shrinkage is an important property for such resins. In dental applications, the phrase “zero polymerization shrinkage” typically means that the stresses accumulated during curing do not debond the dentin-restorative interface or fracture the tooth or restorative, which can result in marginal leakage and microbial attack of the tooth. Low polymerization shrinkage also is important to achieve accurate reproduction of photolithographic imprints and in producing optical elements.
Another advantageous property for such resins is maintenance of a liquid crystalline state during processing. For comfort in dental applications, the resin should be curable at “room temperature,” defined herein as at typical ambient temperatures up to about body temperature. Preferred curing temperatures are from about 20° C. to about 37° C. Mesogens which have been found to polymerize in a relatively stable manner at such temperatures are bis 1,4 [4′-(6′-methacryloxyhexyloxy)benzoyloxy] t-buylphenylene mesogens and their structural derivatives. These mesogens have the following general structure:

Methods for varying the rheology and phase transition temperature of the mesogens, without adversely affecting the mechanical strength and stability of the cured mesogenic resin, are always needed.